Tire non-uniformity relates to the symmetry (or lack of symmetry) relative to the tire's axis of rotation in certain quantifiable characteristics of a tire. Conventional tire building methods unfortunately have many opportunities for producing non-uniformities in tires. During rotation of the tires, non-uniformities present in the tire structure produce periodically-varying forces at the wheel axis. Tire non-uniformities are important when these force variations are transmitted as noticeable vibrations to the vehicle and vehicle occupants. These forces are transmitted through the suspension of the vehicle and may be felt in the seats and steering wheel of the vehicle or transmitted as noise in the passenger compartment. The amount of vibration transmitted to the vehicle occupants has been categorized as the “ride comfort” or “comfort” of the tires.
Tire uniformity characteristics, or attributes, are generally categorized as dimensional or geometric variations (radial run out (RRO) and lateral run out (LRO)), mass variance, and rolling force variations (radial force variation, lateral force variation and tangential force variation, sometimes also called longitudinal or fore and aft force variation). Uniformity measurement machines often measure the above and other uniformity characteristics by measuring force at a number of points around a tire as the tire is rotated about its axis.
Once tire uniformity characteristics are identified, correction procedures may be able to account for some of the uniformities by adjustments to the manufacturing process. Some of the uniformities may be hard to correct during the manufacturing process and so additional correction procedures are needed to correct remaining non-uniformities of cured tires. A number of different techniques may be available, including but not limited to the addition and/or removal of material to a cured tire and/or deformation of a cured tire. Some of the known uniformity correction techniques are limited in their application, for example in precision control and/or in the types of tires that are correctable via such techniques. For example, low profile tires having reduced sidewall height may be particularly difficult to correct using known uniformity correction techniques. Known techniques may also be limited in the type of uniformity parameters that are correctable.
Examples of known systems in which tire material is removed to improve uniformity include U.S. Pat. Nos. 4,041,647 and 5,537,866. U.S. Pat. No. 4,041,647 (Ugo) relates to improving the uniformity of a pneumatic tire by measuring and correcting excessive variation in the free radial run-out of the tire during such rotation of the tire. U.S. Pat. No. 5,537,866 (Bangert et al.) discloses a method for correcting tire imbalance of a tubeless pneumatic tire including in part a step of removing at locations, where the value of a measured radial parameter is greater than the minimum plus the threshold value, tire material from the radially inwardly facing seat surface of the tire bead at least to such an extent that the remaining tire imbalance is within a given tolerance range.
An example of correcting non-uniformities by adding material is disclosed in U.S. Pat. No. 5,060,510 (Rousseau), which discloses a method of correcting the variations of radial force between a tire and the ground, including in part a step of effecting correction by means of wedges in the form of circular rings placed between the mounting rim and the beads of the tire.
Examples of known systems in which tire uniformity is corrected without grinding, but instead by deformation, are disclosed in U.S. Pat. No. 5,616,859 (Rhyne) and U.S. Published Application No. US 2007/0145623 A1 (Hair, J R.). U.S. Pat. No. 5,616,859 (Rhyne) discloses a method and apparatus for reducing the magnitude of a uniformity characteristic in a cured tire, whereby at least a portion of one carcass reinforcing member of the tire is permanently deformed a predetermined amount, for example by variable stretching of at least a portion of a carcass reinforcing member beyond its elastic limit for a predetermined amount of time. U.S. Patent Application Publication No. US 2007/0145623 A1 (Hair, J R.) discloses an apparatus and method for reducing the magnitude of multiple harmonies of uniformity characteristics in a cured tire by utilizing a ring containing multiple plates to permanently deform portions of the carcass reinforcing member of the tire at various identified locations.
In light of the need for providing effective and efficient solutions for correcting non-uniformities in a cured tire, it is desirable to provide a new correction method that offers precision correction control by selective removal at one or more different tire bead locations to correct one or more harmonics of one or more multiple uniformity parameters. Although known technology for uniformity correction has been developed, no design has emerged that generally encompasses all of the desired characteristics as hereafter presented in accordance with the subject technology.